To enable coaxial relative rotation of a pair of elements it is established practice to provide a race body on one element and a bearing body on the other element. The two bodies provide a bearing structure that enables relative rotation to occur between the two elements. The bearing bodies have matching continuous ring-shaped race surfaces to make a friction bearing, or instead have rollers or balls between them to form roller or ball bearings. In any event, damage to either body, and especially to a race, destroys the bearing function, and the system must be repaired, usually by replacing the damaged race.
This may not be much of a problem in conventional machinery in convenient locations. In a factory, a large bearing can be dismantled, the damaged parts removed and replaced, and the bearing reassembled. There is no particular difficulty in what is basically only a time-consuming inconvenience. However, there are installations wherein such a solution is not acceptable. One example is found in relatively large space-based installations. In such locations the physical effort required to repair a structure in this way is often simply not available, and storage of spare parts is not practicable. The need to wait for replacement parts to be sent aloft, or the need for an astronaut to make substantial exertions to repair the structure can cripple a project.
It is necessary to anticipate that serious damage may be done to bearing systems, for example as the consequence of collisions with space junk. Unless the system is inherently provided with means to restore the bearing function without requiring the use of spare or replacement parts, and/or unless it can be repaired with only minimal physical effort, that system is seriously flawed for such applications.
A well-received system which provides for redundancy of bearing sets, so that in the event one bearing set is disabled, another set can be utilized with minimal physical effort and no replacement parts is shown in Benton U.S. Pat. No. 4,761,084, issued Aug. 2, 1988. This patent is incorporated herein in its entirety by reference for its showing of such a system and its desirability. The instant invention is regarded by its inventor as an improvement to the Benton system.
Although the instant system can be utilized in any bearing system in which a ready response is required in the event of failure of a bearing set, its primary utility will be found in applications wherein substantial delay in response is objectionable, and in which access to the failed system is difficult, and in which it is undesirable to have spares at hand for replacement of failed parts. Examples of such installations are battlefield and spacecraft antennas, and space devices such as telescopes, antennas, and direction-sensitive experiments, controls and panels.
However, in all of these, there may be an ultimate need for repair, and for this purpose it is an object of this invention to provide for ready removal and replacement of the rolling bearing portion of the bearing sets, as well as for redundancy of bearing function after failure of one of the races.
While it is acceptable in many installations for two bearing sets to roll simultaneously and in series with one another, there are other installations where for some reason it may be preferred for only one set to run at a time, and to provide readily controlled selector means to select which one. It is an object of this invention to provide means for this purpose. This not only enables the selection of bearing set to be run, but provides for the full disablement of a damaged bearing set, all by remote command.
Bearing systems of the type contemplated by this invention will ordinarily be expected to operate in a wide range of temperatures. Such circumstances often result in binding in conventional bearing systems. The construction of bearing systems according to this invention is susceptible to design wherein its net coefficient of thermal expansion is sensibly near zero, and this is another object of the invention.